Method of producing wood pulp



Patented Jul 1, v1930 UNITED STATES PATENT OFFICE GEORGE E. men, or BROOKLYN, NEW YoRK, AssmNoR, BY DIRECT AND MESNE AS- SIGNMENTS, TO CONSERVATION CORPORATION OF AMERICA, A CORPORATION OF DELAWARE No Drawing.

The present'invention relates to the production of wood pulp or fibrova'scular cellulose from woods and plants, for the manufacture of paper, fibre board, and the like, and the fundamental object of the invention is to provide a novel process for treating the wood in a simple, practical and eflicient manner, in order to remove theextraneous matter and obtain a high grade cellulose fibre of maximum strength, which separates easily, and which will combine or mat perfectly in making paper orfibreboard.

' Another. object is to provide such a method of roducing wood pulp, which is not only hig ly efiicient for well known pulp woods, but which also enables a high grade wood pulp to be obtained from several classes of woods not suitable for wood pulp by prevailing processes, thereby making such additional woods available for high grade pulp which have heretofore been ditficult or impossible to bleach thoroughly. For example, the present process is suitable and eflicient for such woods as Douglas fir, larch, hemlock, Mississippi red gum, Maine spruce, Canadian spruce, Louisiana cypress, Oregon pine, pitch pine, soft maple, resin pine, Kentucky poplar, Hura crepitan; white oak, red oak and soft white pine, some of which, as known to the trade, are considered unsuitable for the productionof a high grade pulp.

A further object is the elimination of the treatment of the wood, as in prevailing proc-. esses, by reagents under pressure, such as in digesters, and the elimination of incidental complicated apparatus and cumbersome handling and maniulation of the materials, and the'present process enables-the wood to be treated, for the extraction of foreignnnatter therefrom, in open tanks under atmospheric/ the purpose of removing the extraneous matter therefrom, such as the starch, sugar, gum,

METHOD OF PRODUCING WOOD PULP Application filed ,Tanuary 24, 1924. Serial No. 688,350.

acid, oil, resin, albumin, tannin, vetc., in order toprepare the Wood for bleaching, without using dangerous reagents or pressure.

The other phase of the process resides in the bleaching of the treated wood in such a way as to be improved and thoroughly efli clent in connection with the first phase of treatment of the wood, in order to obtain a thoroughly'bleached fibre of high grade.

In, carrying out the process, the logs are first prepared by removing the bark and small branches, and the Wood, either the whole logs or sticks or blocks, are then boiled in a saccharine (sugar-like) solution, in order to extract the foreign matter, the term "saccharine being used herein with the ad- ]ective meaning to indicate a sugar or sugarlike solution. Such solution may vary according to the different grades of woodstreated, and according to other circumstances. For example, a typical solution comprises 1,200 pounds of water, 360 pounds of sugar (50% dextrose and 50% levulose) and 75 pounds of prepared dextrin, the sugar and dextrin providing the mixed carbohydrates. These proportions may vary according to the different grades of Woods treated, but the amount of sugar is substantially 25% of the amount of water, and the amount of dextrin is substantially 5% of the amount'of "water. When it is desired that the finished product be insect and fungi proof, and to prevent rot, sodium fluoride is added to such solution amounting to substantially 2% of the total weight of the solution, or for the proportions'given, 32 pounds of sodium fluoride. The specific gravity of such solution at a temperature of about 60 degrees F. would be about 1.090, which Will permit of the solution being thinned according to the-density or absorption characteristics of the wood to be treated. The average specific gravity of the solution, during the treatment, should be between 1.075 and 1.085, and only Water is added for thinning the solution to the desired specific gravity. There is also added to such solution of 1% of soda ash (95%), based on the total weight of the solution, or approximately-2% of the amount of sugar or.

carbohydrate. The addition of sodium sulphite to the solution, in an amount substantially five percent of the solution, has been found to also materially assist in the deresination of the Wood and the bleaching thereof.

Such liquor or solution is heated in any suitable open tank, by means of steam coils or the like, to a temperature that may vary from 100 to 150 degrees F.', and tha wood is then immersed in the solution. The immersing of the wood can be accomplished in different-ways, and the wood can be loaded on trucks, skids or other carriers for conveying the wood into and out of the tank without individually handling the pieces of wood.

When the wood is immersed in the solution, the solution is heated to gradually raise the. temperature to 212 degrees F., or the boiling point of water, and the boiling is continued until all extraneous matters are removed from the wood. During the boiling of the wood, scum and froth rise to the surface, and areskimmed off, and the skimmings are preserved, and are used as fertilizer and other valuable by-products. When the wood has been boiled a suflicient length of time, ranging anywhere from a fraction of an hour to several hours, and no further scum rises to the surface of the liquor, .then the solution is permitted to cool down to not lower than approximately 170 degrees F. and wood is removed. The solution is at once ready for the next load of wood.

The wood is preferably dried before grinding, either naturally or artificially, artificial drying being used for rapid production. Any suitable steam-heated or equivalent dryer can be used.

Thewood is then ground up, either dry or wet, but preferably dry, into small shreds or particles, and is then ready for bleaching.

The saccharine substance used may be a low grade syrup or molasses, either cane, beet or corn, or other form of sugar or invert. When a mixed carbohydrate solution is used, dextrin is mixed with the sugar. The dextrin may be of corn, potato or other dextrinized starch. Black strap molasses-and other low grades of molasses and syrup are used to advantage, being cheap forms of sugar, and containing impurities which are beneficial in the treatment and bleaching of the wood.

' Such 10w grades of molasses and syrups contain sulphur dioxide, which is useful in further preparing the wood for bleaching. In

" fact, the present process enables low grade molasses to be used, whichis not suitable for human consumption, especially when such molasses contains over 350 parts per million of sulphur dioxide,'which is the limit permitted under Government requirements. Molasses and syrups containing sulphur dioxide in excess of such amount can beused'to advantage in the present process, and when the sulphur dioxide content of the molasses or syrup is lower, it can be increased by the addition of sulphur dioxide, so that the saccharine solution contains a desired small percentage of the sulphur dioxide.

During the boiling of the wood in the saccharine solution, the solution enters the pores of the wood by osmotic action, and will dissolve the foreign matter in or expel it from the wood, such as starch, sugar, gum, acid, oil, albumin, tannin, and the like, and as the boiling continues the deleterious or undesirable elements are thus extracted from the wood by the boiling solution, until finally, after the boiling has been continued a required length of time, the wood is near a condition of pure cellulose, containing only such small remaining portion of the solution as can be readily eliminated in the bleaching step. The sugar or saccharine solution has the ability, by osmotic action, to penetrate the colloidal cell walls of the wood, with an efficiency that is not possible with water alone or ,with other, substances previously suggested or used in the art. The osmotic action, is of considerable benefit in penetrating the cell walls, without using a closed tank, in order that the foreign matter may be dissolved, or discharged from the cells. During the boiling action, the lignin components of the wood are removed ;.portions of actual inor crusting matters are gelatinized and converted into colloidal condition; the starches and gummy matters are removed; and the saps and natural moisture arevaporized. The extraneous matters are eliminated without discoloring the cellulose, and the treatment does not weaken the fibres as in prevailing processes, whereby the fibers have maximum strength. Some of the foreign matter rises to the surface of the solution as scum and is skimmed off, and the balance leaves as vapor. The presence of the soda ash in the solution will, by a neutralizing'action on the acid in the wood, form a sodium salt, the nature of which depends on the particular acid in the wood, and in the react-ion that I takes place, carbon dioxide isliberated, which helps or assists in expelling loosely or mechanically combined substances present in the wood.

.The' same treatment is used for plants which are of a woody or semi-woody nature, and which are available for the production of fibre pulp. The pulp produced from the wood or plant may not only be used for making paper, fibre and wall board, and the like, but may also be used for the production of pure cellulose to be used for the manufacture of fibre silk, gun powder, etc. The cellulose of the wood or plants being extremely inert or non-reactive, resists the hydrolyzing action of alkalis and acids, and has no tendency to combine directly with the halogen elements (chlorine and bromine) so that the desired element of the wood (cellulose) 'remains unaffected by the treatment to which the wood is subjected in the present process.

For some Woods, black strap molasses and corresponding low grades of molasses and syrups can be used alone, with water, Without the addition of dextrin. For example, three and one-half pounds of such low grade molasses or syrup is used with each gallon of water. and the sulphur dioxide content-of the molasses or syrup makes such molasses or syrup especially suitable and advantageous for the present process, inasmuch as the sulphur dioxide or sulphite, during the boiling of the wood in the solution, is distributed throughout the wood in minute quantity,

and, by the formation of sulphuric acid, will I attach and remove foreign matter in the wood which may'not be affected by the saccharine. The wood is therefore better prepared for the bleaching step.

The ground up treated wood is then bleached, preferably after the fibre has been dried, although the wet fibre can be bleached with success. The bleaching is done by means of the action of a sodium or calcium hypochlorite solution on the coloring material remaining in the wood. The action differentiates from prevailing bleaching processes, in so far as mechanical procedure is concerned, inasmuch as it is necessary to only have a slight mechanical agitation, and the bleaching is done at a temperature not exceeding degrees F. The manufacture of the hypochlorite solution may be by any of the well known methods, but electrolytic hypochlorite is especially suitable, notably when a complete bleaching action is desired. The

" fibre is introduced into the solution of hypo- .chlorite, and is allowed to remain therein from four to twelve hours, dependent on the type of woodthat is being bleached. Only slight mechanical agitation is necessary, and

the bleaching action will removethe last traces of coloring and foreignmatters from the fibre, with the result of a perfectly bleached fibre or pure cellulose.

After the fibre is bleached, it is removed from the bleaching solution, and is then.

Washed thoroughly in water, and dried. The cellulose thus produced can then be used at once for the production of paper, fibre board, gun powder, artificial silk, etc.

The sodium sulphite,- when added to the saccharine solution, will also assist materially in the bleaching of the Wood, in addition to deresinating the wood during the boiling thereof.

Having thus described the invention, what is claimed as new is 1. The process of producing wood pulp, consisting in boiling wood in water containing a substantial proportion of one or more carbohydrates, until no further scum rises to the surface, and then bleaching the wood.

2. The process of producing wood pulp,

consisting in boiling wood in water containing a substantial proportion of one or more carbohydrates and also containing sodium fluoride, soda ash and sodium sulphite, and then bleaching the wood.

3. The process of producing wood pulp, consisting in boiling wood in water containing a substantial proportion of one or more carbohydrates and also containing sodium fluoride, and thenbleaching the wood.

at. The process of producing wood pulp,

consisting in boiling wood in water containing a substantial proportion of one or more carbohydrates and also containing soda ash in an amount approximately 2% of the amount of carbohydrate, and then bleaching the Wood.

5. The process of producing wood pulp, consisting in boiling wood in water containing a substantial proportion of one or more carbohydrates and also containing sodium sulphite, and then bleaching the wood.

6. The process of producing wood pulp, consisting in boiling wood in water contain- "ing a substantial proportion of sugar, until no further scum rises to the surface, and then bleaching the wood.

7. The process of producing wood pulp,

consisting in boiling wood in water containing a substantial proportion of sugar and also containing sodium fluoride, soda ash and sodium sulphite, and then bleaching the wood.

8. The process of-producing wood pulp, consisting in boiling wood in water containing a substantial proportion of sugar and also containing sodium fluoride, and then bleaching the wood.

9. The process of producing wood pulp, consisting in boiling wood in water contaming a substantial proportion of sugar and also containing soda ash in an amount approximately 2% of the amount of sugar and then bleaching the wood.

10. The process of producing wood pulp, consisting in boiling wood in water containing a substantial proportion of sugar and also containing sodium sulphite, and then bleaching the wood.

In testimony whereof I hereunto aflix my 

